A teenager was killed by a prescription drug 50 times stronger than heroin, a toxicology report has confirmed.

Results returned this week show Robert Fraser took fentanyl, the painkiller American singer Prince overdosed on.

The 18-year-old, from Deal in Kent, was found dead in his bedroom in November.

His mother, Michelle Fraser, said parents need to be aware that people are experimenting with black market prescription substances without knowing the risks.

The synthetically-produced opiate is faster acting than heroin. America's Drug Enforcement Agency (DEA) labelled it as a "threat to public safety" after a huge surge in related deaths.

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Michelle Fraser said parents must be more aware of the dangers of prescription drugs

Speaking for the first time since his death, Ms Fraser said: "This day and age, our teenagers - whether we want to accept and believe it or not - are dabbling in stuff.

"It's so easy. They get it on the internet, they've got mobile phones. My generation wasn't as aware, but we need to be now, for our children."

Three of Robert's friends also took the drug, but survived. Ms Fraser believes they were naive about what they were buying.

Mike Trace, chief executive of the Rehabilitation for Addicted Prisoners Trust (RAPt), said the line is blurring between legal, illegal and prescription drugs and "many substances being sold are not as benign as dealers claim them to be".

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Michelle Fraser with her son Robert

Robert's friend Kian Philpott, 16, said: "He was the happiest person and good at anything he tried - skateboarding, bikes, he always succeeded, as well as being in a band."

Ms Fraser said her son was "affectionate" and "loving" and somebody who "always looked after others".

She added: "Robert should be getting an apprenticeship, a girlfriend, eventually having a family. He won't be doing any of that now."